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31.1.11

How to be a neuroscientist

In this post, I will teach you all how to be proper, skeptical neuroscientists. By the end of this post, not only will you be able to spot "neuro nonsense" statements, but you'll also be able to spot nonsense neuroscience questions.

I implore my journalist friends to take note of what I say in this post.

Much has already been said on the topic of modern neuroimaging masquerading as "new phrenology". A lot of these arguments and conversations are hidden from the lay public, however, so I'm going to expose the dirty neuroscientific underbelly here.

In study after study, scientists have found that the striatum lit up like an inferno of activity when people didn’t know exactly what was going to happen next, when they were on the verge of solving their mystery and hoped to be rewarded—it was more active then, in fact, than when people received their reward and had their curiosity satisfied.

"So," you may ask, "what's wrong with that answer? That seems reasonable and sound and very sciencey!"

I can prove, with one statement, that this answer is wrong (if you're impatient, jump to point 2 at the bottom).

I'm not picking on the person who answered the question; they had no way to know. They were just following the discourse of the media narrative about neuroscience findings.

So what is wrong with this explanation (he says, finally getting to the damned point)? I'll break both of these points down in detail later.

1. The question is phrased in such a way that it presumes that "curiosity" is a singular thing.

2. The question presumes that a complex behavior or emotion can be localized to a brain region or regions. There are several philosophical pitfalls packaged into the answer, such as the ontological commitment to the narrative of cognitive neuroscience and the cerebral localization of function.

To be clear, what I'm not saying is that behaviors aren't in the brain. What I am saying is that the cerebral localization narrative is too simplistic.

Let me break down these points.

1. "Is curiosity a singular thing?"
When you ask "where is curiosity in the brain" you assume that researchers can somehow isolate curiosity from other emotions and behaviors in a lab and dissect it apart. This is very, very difficult, if not impossible. Neuroimaging (almost always) relies on the notion of cognitive subtraction, which is a way of comparing your behavior or emotion of interest (curiosity) against some baseline state that is not curiosity.

The underlying assumption in these studies is that activity in brain networks alters in a task-dependent manner that becomes evident after averaging many event-related responses and comparing those against a baseline condition. Deviations from this baseline reflect a change in the neuronal processing demands required to perform the task of interest.

Imagine asking "where is video located in my computer?" That doesn't make any sense. Your monitor is required to see the video. Your graphics card is required to render the video. The software is required to generate the code for the video. But the "video" isn't located anywhere in the computer.

Now there's a subtlety here. It may be that people with damaged striata have curiosity impairments (whatever that means), which would agree with the fMRI study discussed in that link above, but it proves that the striatum is not where curiosity is in the brain. More technically: the striatum may be a critical part of a network of brain regions that support curiosity behaviors, but that is different from saying that the striatum is where curiosity is.

Or, as I say in my chapter:

...the cognitive subtraction method... provide[s] details of functional localization that can then be tested and corroborated using other methodologies, including lesion studies. The interpretation of these localization results is confounded, however, by a lack of clarity in what is meant for a "function" to be localized. For example, Young and colleagues (2000) noted that for a given function to be localizable that function "must be capable of being considered both structurally and functionally discrete"; a property that the brain is incapable of assuming due to the intricate, large-scale neuronal interconnectivity.

Thus, discussing behavioral functions outside of the context of the larger cortical and subcortical networks involved with that function is a poorly posed problem. Therefore, the scientific study of cognition requires detailed neuroanatomical and connectivity information to compliment functional activity findings.

God. I was going to end this with some links to news stories talking about neuroscientists finding out where (love/happiness/hate/prejudice/sexytimes/etc.) were located in the brain, but I just gave up. There are some damned many of them.

If you're a journalist and you're reading this, please change the way you talk about these results.

If you're a student, if you remember nothing else from this post, just remember to ask, "can a person who has a lesion to that brain region not experience that emotion or do that behavior anymore?" If the person still can, then that is not where that behavior is located in the brain. And, in all likelihood, that function can't be localized to any one region at all.

17 comments:

Thanks for the post Bradley. Very interesting. I just checked the original question on Quora and your answer is on top! I registered on Quora just to vote up your answer; not that it needs my vote to be on top. Cheers!

Hold on, no "poof" just yet! You forget a big possibility that would be consistent with both the conclusion that the striatum is responsible for curiosity and the observation that patients with striatum lesions still have possible unimpaired curiosity -- plasticity! i.e., a specific structure could very well be responsible/necessary for a given function in normal brains, but if it gets damaged, other parts of the brain can compensate.

Not that I think that this actually happens in the case of curiosity/striatum, or that media coverage of neuroimaging findings is well-informed, but your lesion study alone may not disprove the hypothesis. :)

Excellent post! Sometimes I wonder if functional imaging has actually set back progress in understanding the brain as asking "where" questions seems productive, but actually keeps us from asking the real "how" questions.

Thanks Dean & Michelle! Dean, great post, by the way. Michelle, I couldn't agree more. Neuroscientists often confuse knowing what regions are associated with a behavior with understanding that behavior.

Sarang: Touché. :) BUT, that's likely only true if there is time for reorganization, unless the information rerouting happens *very* quickly. If you examine someone with a striatal lesion in the acute stroke phase and they still show curiosity, then I think we're back to "hypothesis poofing" territory.

I always try to avoid using the following terms in regard to an aspect of cognitive function X and the brain:

Causes Xis responsible for Xis the part of the brain that *does* X

and instead I always try to say:

(For neuroimaging studies)is associated with X

(For lesion studies)is critical to the function of X but not necessarily sufficient for X

It always takes a couple of minutes to explain what I mean, but its worth it in the end, as people always get what I'm talking about, at least when I give examples, rather than talking abstractly as I've done here.

In lectures, I like to cite the dead Salmon brain activity study, as well as the voodoo correlations papers when talking about over reliance on neuroimaging studies.

I think people want quick, pat answers that work forever...I just heard a couple segments this weekend on Wisconsin Public Radio: a series stemming from Carl Jung's Red Book...I'm sure you have heard it. Frick's book was also mentioned. Thanks for writing....

Very Nice post. When I was in college, I barely study neuroscience, and one of my favourit scientist was Gerard edelman. I' m not up to date in neuroscience, but, the theory of neural group selection doesnt give Nice insigths about the intricate net that are the higher brain functions? (as cousciouness).

I may be speaking crap, but the TSGN came to my mind anile I read the post.

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Who I Am

Neuroscientist combining large scale data-mining, machine-learning techniques, and brain computer interfacing with hypothesis-driven experimental research to understand the relationships between the human frontal lobes, cognition, and disease. Into really geeky stuff. World zombie neuroscience expert. Also run brainSCANr.com with my wife, Jessica.